Underwater Missile-borne Ultrasonic Detection Of The Transmitted Signal Direct Digital Frequency Synthesis And Implementation

Facing the future battlefield situation, the airborne depth bomb and the ship-based rocket bomb still play an important role in the short-range antisubmarine weapons which are used in the epeiric seas. For the modern fuzes of the weapons, it will improve the damage ability of ammunition or warhead effectively if their intelligentized on-board object detecting sets can search for, locate and track the objects automatically so as to provide more information for the firing system of the fuzes.The supersonic sounding technology is widely used in underwater on-board object detecting sets of the modern fuzes. But because of the narrow search range, they can only find the object with the traditional technology. They must be intelligentized so as to obtain the information of objects rapidly from the target echo and accomplish the mission of searching for, orientating and locating the object. Our county was developing the underwater on-board supersonic detecting set. By simulating the cry and audition function of bats, it could orientate, track and locate the objects rapidly and precisely. The generation of digital transmitting signal which is controlled by the system processing center is one of the key researching questions, especially the modulation method of transmitting signal which directly influences the resolution of detectors.Because the digital signal has the following advantages:less error of transmitting and processing, easily extracting the waveform information and characteristic, easily reconstruct-ing signal. By the on-board characteristic of the fuze detector, the thesis designs the signal generator using the DDS technology which generates symmetric triangular linear frequency modulated pulse signal so as to reduce the signal distortion and improve the resolution of the detecting system.The thesis analyzes the frequently-used transmitting signals(CW, LFM, HFM and PR) and compares the resolution of distance and velocity with each other detailedly; The thesis analyzes several kinds of methods which generate LFM signal and the theory of signal generation with DDS technology; The thesis uses the microcontroller and AD9852 chip to design the hardware system of the signal generator and makes the experimental verification.The experiment results show that the signal generator meets the design requirements.